The invention relates to a measuring arrangement for measuring a pressure signal from a living body, which measuring arrangement comprises a sensor structure comprising a converter for converting the effect of the pressure signal measured from the body to an electrical signal.
The invention is applied in particular to wristband-type heart rate monitors which by means of the measuring arrangement measure the pressure pulse signal of the wrist artery and, on the basis thereof, determine the heart rate. Another field of application is the pressure pulse measurement required in blood pressure measurement. The invention is especially well suited for multi-channel measurement, in which the sensor structure of the measuring arrangement comprises several measuring channels.
In known measuring arrangements the sensor, i.e. in practice, the converter in the sensor, is flat and in direct contact with skin. The measuring point, such as the area of the wrist artery, is, however, an area which does not allow a flat sensor to settle well enough against the skin. This problem is accentuated in multi-channel sensors in which the sensor is considerably wider than in one-channel sensors. A flat sensor also provides the disadvantage that, by means of it, it is not possible to mechanically amplify the signal that is transmitted from the artery to the signal converter. Thus, the drawback in known measuring arrangements is too poor a measuring sensitivity.
It is thus an object of the invention to develop a novel measuring arrangement so as to reduce the problems and drawbacks related to the known solutions.
To achieve the above-mentioned objective, the measuring arrangement of the invention is characterized in that it comprises a pressure transmission structure prior to the converter in the sensor structure, the pressure transmission structure comprising one or more pressure transmission elements, and which pressure transmission structure is, through one or more pressure transmission elements, meant to be in direct or indirect contact with the body for detecting the pressure signal measurable from the body, and which pressure transmission structure is, through one or more pressure transmission elements, connected to the converter for transmitting the effect of the pressure signal detected in the body to the converter in the sensor structure by means of one or more pressure transmission element.
The idea of the invention is based on a pressure transmission structure implemented by means of one or more pressure transmission elements, and its suitable design.
The method and arrangement of the invention provide the advantage that the sensor settles better than before against the measuring point, for instance against the wrist at the wrist artery. The invention also in a way raises what is known as the sensitive surface of the sensor to a sufficient distance from the converter in the measuring arrangement and the other structures whose operation involves electrical signals. The sensitive surface of the sensor, i.e. the pressure transmission elements, is on the surface of the measuring arrangement, but the structures whose operation involves electrical signals can be kept deeper in the apparatus and thus at a distance from the skin and better protected against the loads from the operating environment. In addition, a preferred embodiment of the invention provides mechanical amplification for the effect of a pressure signal, which effect is transmitted from the first edge of the pressure transmission element through the second edge of the element to the signal converter. The-preferred embodiments of the invention emphasize the advantages provided by the basic invention.